全文获取类型
收费全文 | 1818篇 |
免费 | 81篇 |
国内免费 | 6篇 |
专业分类
测绘学 | 76篇 |
大气科学 | 136篇 |
地球物理 | 388篇 |
地质学 | 722篇 |
海洋学 | 134篇 |
天文学 | 289篇 |
综合类 | 8篇 |
自然地理 | 152篇 |
出版年
2024年 | 5篇 |
2023年 | 12篇 |
2022年 | 10篇 |
2021年 | 30篇 |
2020年 | 46篇 |
2019年 | 44篇 |
2018年 | 55篇 |
2017年 | 77篇 |
2016年 | 91篇 |
2015年 | 60篇 |
2014年 | 58篇 |
2013年 | 120篇 |
2012年 | 79篇 |
2011年 | 97篇 |
2010年 | 108篇 |
2009年 | 101篇 |
2008年 | 104篇 |
2007年 | 90篇 |
2006年 | 92篇 |
2005年 | 84篇 |
2004年 | 88篇 |
2003年 | 58篇 |
2002年 | 61篇 |
2001年 | 35篇 |
2000年 | 23篇 |
1999年 | 38篇 |
1998年 | 20篇 |
1997年 | 16篇 |
1996年 | 17篇 |
1995年 | 6篇 |
1994年 | 21篇 |
1993年 | 14篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 7篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 15篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1974年 | 4篇 |
排序方式: 共有1905条查询结果,搜索用时 31 毫秒
81.
Christian Sellar 《GeoJournal》2013,78(1):1-19
This paper analyzes how processes of Europeanization opened up opportunities and generated ideals, which in turn changed the articulation between political and economic powers in the city and county of Timisoara, Western Romania. It builds on case studies of local government agencies and foreign investors from Italy. In doing so, it discusses the circular relationship between the European and the local levels of governance: European governance affected the interactions between firms and institutions in the city, while at the same time city authorities used different understandings of ‘Europe’ to pursue their own agenda. It also shows some of the unexpected side-effects of Europeanization, due to the political activism of Italian investors. Beck and Grande’s concept of ‘reflexive modernization’ and the literature on regional economies frame the discussion. 相似文献
82.
83.
Roberto Ventura Santos Edilton J. dos Santos João Adauto de Souza Neto Luis Christian Montreuil Carmona Alcides Nóbrega Sial Luis Henrique Mancini Lauro Cézar Montefalco de Lira Santos Gilzênia Henrique do Nascimento Lucas UpaDafubigin Santos Mendes Emerson Marcello Ferreira Anastácio 《Gondwana Research》2013,23(1):380-389
Strongly-deformed marbles may be easily confused with linear and elongated carbonatite intrusions. Both rocks may present similar texture and foliation to the host rock, or even cross cutting field relationships, which could be interpreted either as igneous or high-grade metamorphosed marble. Diagnostic criteria are even more complex when there is evidence of melting of the metasedimentary carbonate rock, such as has been described in the Himalayas and in the Eastern Ghats, India.In the Alto Moxotó Terrane, a high-grade gneissic domain of the Borborema Province, Northeastern Brazil, there are metacarbonates associated with banded gneisses and different metaplutonic rocks. Field evidence indicates the absence of other metasedimentary rocks associated with these marbles, thus suggesting that these carbonates were separated from other siliciclastic metasedimentary rocks. The presence of marble also suggests that it may represent the initial stage of a crustal carbon recycling into the mantle. These marbles present many field similarities to carbonatites (e.g., fluid-flow structure) and, together with metagranites and metamafic intrusions, may represent a major collisional tectonic suture.A detailed study of the carbon, oxygen and strontium isotopic composition of these marbles is presented. This study aims to identify the origin of the different isotopic components. It is argued that these rocks were subjected to temperature and pressure conditions that were sufficiently high to have melted them. The isotopic data presented here support this interpretation and indicate the mixing of two components: (i) one characterized by radiogenic Sr isotopes and mantle-like carbon isotopes, which is associated with the gneissic and mafic rocks, and (ii) another characterized by low 87Sr/86Sr ratios and highly positive δ13C values. Available geochemical data for the upper Paleoproterozoic indicate that the 87Sr/86Sr ratio of ocean water, varying between 0.7050 (2.25 ± 0.25 Ga) and 0.7047 (1.91 Ga), falls within the lower range of the samples from Itatuba and thus reinforces the interpretation that these marbles are sedimentary-derived and were partially contaminated by interaction with the host gneissic and mafic rocks. 相似文献
84.
Coesite and pure pyrope in high-grade blueschists of the Western Alps: a first record and some consequences 总被引:55,自引:0,他引:55
Christian Chopin 《Contributions to Mineralogy and Petrology》1984,86(2):107-118
A pyrope-quartzite originally described by Vialon (1966) from the Dora Maira massif was resampled and reinvestigated. Garnet (up to 25 cm in size), phengite, kyanite, talc and rutile are in textural equilibrium in an undeformed matrix of polygonal quartz. The garnet is a pyrope-almandine solid solution with 90 to 98 mol % Mg end-member. It contains inclusions of coesite which has partially inverted to quartz, resulting in a typical radial cracking of the host garnet around the inclusions. Several lines of evidence show that coesite crystallised under nearly static pressure conditions and that the whole matrix has once been coesite. The formidable pressures of formation implied (≧28 kbar) are independently indicated by i) the coexistence of nearly pure pyrope with free silica and talc, ii) the coexistence of jadeite with kyanite, iii) the high Si content of phengite. Water activity must have been low. The stability of talc-phengite and the presence of rare glaucophane inclusions in pyrope point to low formation temperatures (about 700 °C) and to a probable Alpine age for the assemblage. This is evidence that low temperature gradients, how essentially transient they are, may nevertheless persist to considerable depths. Moreover, the upper crustal (evaporite-related?) origin of the quartzite and its interbedding within a continental unit implies that continental crust may also be subducted to depths of 90 km or more. The return back to the surface is problematic; the retrograde assemblages observed show that it must be tectonic. If the rocks remain at depth, new perspectives open for the genesis of intermediate to acidic magmas. Eventually, the role of continental crust in geodynamics may have to be reconsidered. 相似文献
85.
The configuration of Alpine accumulation areas during the last glacial maximum (LGM) has been reconstructed using glacial–geological mapping. The results indicate that the LGM ice surface consisted of at least three major ice domes, all located south of the principal weather divide of the Alps. This implies that the buildup of the main Alpine ice cover during oxygen isotope stage (OIS) 2 was related to precipitation by dominant southerly atmospheric circulation, in contrast to today's prevalent westerly airflow. Such a reorganization of the atmospheric circulation is consistent with a southward displacement of the Oceanic Polar Front in the North Atlantic and of the associated storm track to the south of the Alps. These results, combined with additional paleoclimate records from western and southern Europe, allow an interpretation of the asynchronous evolution of the different European ice caps during the last glaciation. δ18O stages (OIS) 4 and 3 were characterized by location of the Polar Front north of 46°N (Gulf of Biscay). This affected prevailing westerly circulation and, thus, ice buildup in western Scandinavia, the Pyrénées, Vosges, and northern Alps. At the LGM, however, the Polar Front lay at 44°N, causing dominating southerly circulation and reduced precipitation in central and northern Europe. 相似文献
86.
Stefan Strasky Angela A. Graf Zhizhong Zhao Peter W. Kubik Heinrich Baur Christian Schlüchter Rainer Wieler 《Journal of Asian Earth Sciences》2009,34(3):458-465
The sensitivity of Tibetan glacial systems to North Atlantic climate forcing is a major issue in palaeoclimatology. In this study, we present surface exposure ages of erratic boulders from a valley system in the Hengduan Mountains, southeastern Tibet, showing evidence of an ice advance during Heinrich event 1. Cosmogenic nuclide analyses (10Be and 21Ne) revealed consistent exposure ages, indicating no major periods of burial or pre-exposure. Erosion-corrected (3 mm/ka) 10Be exposure ages range from 13.4 to 16.3 ka. This is in agreement with recalculated exposure ages from the same valley system by [Tschudi, S., Schäfer, J.M., Zhao, Z., Wu, X., Ivy-Ochs, S., Kubik, P.W., Schlüchter, C., 2003. Glacial advances in Tibet during the Younger Dryas? Evidence from cosmogenic 10Be, 26Al, and 21Ne. Journal of Asian Earth Sciences 22, 301–306.]. Thus this indicates that local glaciers advanced in the investigated area as a response to Heinrich event 1 cooling and that periglacial surface adjustments during the Younger Dryas overprinted the glacial morphology, leading to deceptively young exposure ages of certain erratic boulders. 相似文献
87.
88.
Jean-Jacques Macaire Christian Di-Giovanni Florent Hinschberger 《Comptes Rendus Geoscience》2005,337(8):735-744
Accumulation of organic matter in fens of fluvial valleys is often related to a low terrigenous matter delivery and to palaeoenvironmental conditions inducing low mechanical erosion. These assumptions come from the interpretation of contents in organic (MO) and mineral (MM) matters in sediments, expressed in percents, and then exactly anticorrelated. Calculation of mass accumulation rates of MO and MM , expressed in g?m?2?yr?1, shows that and generally are not anticorrelated and that high values of and could appear simultaneously. That expression of MO and MM accumulation makes it possible to precise the climatic and human impact on sedimentation. To cite this article: J.-J. Macaire et al., C. R. Geoscience 337 (2005). 相似文献
89.
Modelling of Tsunami Propagation in the Vicinity of the French Coast of the Mediterranean 总被引:2,自引:0,他引:2
The problem of tsunami-risk for the French coast of the Mediterraneanis discussed. Historical data of tsunami manifestation on the French coast are described and analysed.Numerical simulation of potential tsunamis in the Ligurian Sea is done and the tsunami wave heightdistribution along the French coast is calculated. For the earthquake magnitude 6.8 (typical value forMediterranean) the tsunami phenomenon has a very local character. It is shown that the tsunami tide-gaugerecords in the vicinity of Cannes–Imperia present irregularoscillations with characteristic periodof 20–30 min and total duration of 10–20h.Tsunami propagating from the Ligurian sea to the west coastof France have significantly lesser amplitudes and they are more low-frequency (period of 40–50min).The effect of far tsunamis generated in the southern Italy and Algerian coast is studied also, thedistribution of the amplitudes along the French coast for far tsunamis is more uniform. 相似文献
90.
First attempts towards an integrative concept for the ecological assessment of groundwater ecosystems 总被引:1,自引:0,他引:1
Healthy aquifers deliver important ecosystem services, e.g. the purification of infiltrating water and the storage of high-quality water over decades in significant quantities. The functioning of terrestrial and surface aquatic ecosystems directly depends on groundwater and vice versa. Nowadays, legislation has started to consider groundwater not only as a resource but as a living ecosystem. The assessment of ecosystems requires consideration of ecological criteria, which, so far, are not available for groundwater systems. In the framework of a project supported by the German Federal Environment Agency (UBA), a first concept for the ecological assessment of groundwater ecosystems is developed. Steps to be taken are introduced, with a strong focus on microbes as potential bioindicators. These include (1) the typology of groundwater ecosystems, (2) the derivation of natural background values, (3) the identification of potential bioindicators, and (4) the development of an assessment model. First successes and difficulties associated with these challenges, e.g. the lack of simple correlations between abiotic and biotic variables, are discussed on the basis of a data set from a local and regional aquifer in NE Germany. The need for collaboration between ecologists, hydrogeologists and geochemists, as well as the application of modern approaches such as multivariate statistics, is emphasized. 相似文献